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Differential thermal investigation of the system tricalcium silicate :
calcium lignosulfonate : water in the presence of tricalcium aluminate
and its hydrates
Ramachandran, V. S.
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THERMAL ANALYSIS
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VOL. 2.
PROCEEDINGS THIRD ICTA DAVOS 1971 255D I F F E R E N T I A L T H E R M A L INVESTIGATION O F T H E S Y S T E M T R I C A L C I U M S I L I C A T E - CALCIUM LIGNOSULFONATE
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W A T E RIN T H E P R E S E N C E O F T R I C A L C I U M A L U M I N A T E AND ITS HYDRATES
I b y V. S . R a m a c h a n d r a n D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l , O t t a w a , C a n a d a . A B S T R A C T T h e h y d r a t i o n k i n e t i c s of t r i c a l c i u m s i l i c a t e (C3S) i n t h e p r e s e n c e of c a l c i u l f o n a t e ( C L S ) a n d v a r i o u s o t h e r a d d i t i v e s is f o l l o w e d b y s t i m a t i o n of t h e C a ( O H ) , f o r m e d : H y d r a t i o n of C3S is p l e t e l y i n h i b i t e d i n t h e p r e s e n c e of 0. 5 t o 0. 8 p e r c e n t CLS. A d d i - of 5 p e r c e n t t r i c a l c i u m a l u m i n a t e ( C 3 A ) is s u f f i c i e n t t o p r o m o t e t h e h y d r a t i o n of C3S, s l o w l y a t f i r s t a n d n o r m a l l y a f t e r 3 d a y s . T h e h e x a g o n a l p h a s e c o n t a i n i n g a m i x t u r e of 4 C a 0 . A 1 2 0 3 . 1 3H,O a n d 2 C a 0 . A 1 , 0 3 . 8 H 2 0 is l e s s e f f i c i e n t t h a n C 3 A i n c o u n t e r a c t i n g t h e i n h i b i t i v e a c t i o n of C L S , t h e c u b i c p h a s e ( 3 C a 0 . A 1 , 0 3 . 6 H 2 0 ) b e i n g p r a c t i c a l l y i n e f f e c t i v e . T h e i n h i b i t i v e i n f l u e n c e of C L S is m o r e p r o n o u n c e d w h e n a d d e d t o a m i x t u r e of C3S a n d C 3 A p r e - h y d r a t e d f o r a few m i n u t e s . T h e r e s u l t s a r e e x p l a i n e d o n t h e b a s i s of t h e e x t e n t of i r r e v e r s i b l e 1 u p t a k e of C L S i n t h e o r d e r C 3 A
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h e x a g o n a l p h a s e > c u b i c p h a s e . INTRODUCTION P o r t l a n d c e m e n t c o m p r i s e s f o u r m a i n phases:::, t r i c a l c i u m s i l i c a t e ( C 3 S ) , f3-
d i c a l c i u m s i l i c a t e( B
- C 2 S ) , t r i c a l c i u m a l u m i n a t e ( C 3 A ) , a n d f e r r i t e p h a s e ( c o m p o s i t i o n b e t w e e n C 2 F a n d C , A 2 F , w i t h a n a p p r o x i m a t e c o m p o s i t i o n of C , A F ) , w i t h a few p e r c e n t g y p s u m . S u r f a c e a c t i v e s u b s t a n c e s s u c h a s c a l c i u m l i g n o s u l f o n a t e a d d e d i n s m a l l q u a n t i t i e s t o a c o n c r e t e m i x a r e known t o c o n f e r c e r t a i n b e n e f i c i a l e f f e c t s i n t e r m s of w a t e r r e d u c t i o n a n d s e t r e t a r d a t i o n . A d m i x t u r e s m a y i n f l u e n c e t h e c o m p l e x r e a c t i o n s i n c e m e n t b y m o d i f y i n g t h e r a t e , m o r p h o l o g y , c h e m i c a l n a t u r e a n d o t h e r p r o p e r t i e s of t h e p r o d u c t s . It is u s e f u l t o g a i n a n i n i t i a l u n d e r s t a n d i n g of t h e s i n g l e , X'Norn e n c l a t u r e i n c e m e n t c h e m i s t r y : C = C a O , S = S i 0 2 , A = A 1 2 0 3 , F = F e 2 0 3 , H = H 2 0b i n a r y and t e r n a r y s y s t e m s and then t o extend t h e study t o c e m e n t itself. Studies of the h y d r a t i o n of the individual p h a s e s of p o r t l a n d c e m e n t h a v e r e v e a l e d that even a s m a l l amounL of calcium lignosulfonate (CLS) i s
enough to s u p p r e s s hydration of C3S w h e r e a s i t only r e t a r d s hydration of C3A ( 1 ) . A s m a l l addition of C3A to t h e C3S-CLS-H,O s y s t e m , however, p r o m o t e s hydration of C3S ( 2 ) .
T h e hydration of C3A under n o r m a l conditions p r o c e e d s through the f o r m a t i o n of t h e hexagonal m e t a s t a b l e h y d r a t e s (C4AHx - C,AHx) ,
t h e s e converting to t h e s t a b l e cubic p h a s e ( C , A H s ) . E a r l i e r w o r k on the influence of CLS on t h e above p h a s e s indicated t h a t t h e C3A p h a s e c o n s u m e s l a r g e quantities of CLS, the hexagonal p h a s e i r r e v e r s i b l y a d s o r b s about 10 p e r cent CLS at a n equilibrium c o n c e n t r a t i o n of 0 . 1 5 g / l O O m l , and t h e cubic p h a s e about 2. 0 p e r cent at t h e s a m e equilibrium concentration ( 3 , 4). In addition, changes in morphology, solubility, s u r f a c e a r e a and t h e r m a l behaviour can be o b s e r v e d . On t h i s b a s i s and a s a r e s u l t of s e v e r a l new e x p e r i m e n t s , v a r i o u s a s p e c t s of t h e h y d r a t i o n of C3S i n t h e p r e s e n c e of CLS and additives such a s C,A, C,AHx-C,AHx , C3AHe and h y d r a t e d C3S w e r e investigated by DTA. Work was a l s o done on prehydrated s a m p l e s t o i n t e r p r e t the effects of delayed addition of CLS t o t h e C3S-C3A-H,O s y s t e m . T h e s e r e s u l t s a r e now r e p o r t e d i n t h e hope t h a t t h e y m a y p r o m o t e a b e t t e r understanding of t h e c o m p l e x r e a c t i o n s o c c u r r i n g i n the p o r t l a n d c e m e n t - CLS- H,O s y s t e m . EXPERIMENTAL S a m p l e s T r i c a l c i u m s i l i c a t e w a s p r e p a r e d by calcining a m i x t u r e of CaCO, and SiO, ; it had a Blaine value of 3310 s q ~ m / ~ . T h e C3A p r e p a r a t i o n was obtained by calcination of CaCO, and A l z 0 3 ; t h e s a m p l e had a Blaine value of 4350 s q ~ m / ~ . The hexagonal p h a s e containing a m i x t u r e of C4AHx-C,AHx w a s p r e p a r e d by hydration of C3A in e x c e s s w a t e r a t 2 ° C f o r 5 days with continuous s t i r r i n g . T h e cubic p h a s e (C3AHe) was obtained by s t e a m c u r i n g of C3A at a p r e s s u r e of 100 l b / s q cm f o r 24 h o u r s . T h e h y d r a t e d C3S, r e f e r r e d t o a s H-C3S in t h i s p a p e r , was m a d e by hydrating C3S a t a w a t e r / s o l i d r a t i o of 0. 5 for about 2 y e a r s . T h i s p r e p a r a t i o n w a s a m i x t u r e of calcium s i l i c a t e h y d r a t e and calcium hydroxide. Calcium lignosulfonate (CLS) in t h e f o r m of powder w a s supplied by Lignosol C h e m i c a l s L t d . , Quebec.
P r e p a r a t i o n of P a s t e s
B r o a d l y t h r e e groups of s a m p l e s w e r e p r e p a r e d by h y d r a t i o n for p e r i o d s ranging f r o m one t o 28 days.
T H E R M A L ANALYSIS
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VOL. 2 257 ( i i ) C,S h y d r a t e d i n t h e p r e s e n c e of 5 p e r c e n t a d d i t i v e s s u c h a s C 3 A , h e x a g o n a l p h a s e , c u b i c p h a s e a n d H - C 3 S ; ( i i i ) C 3 S h y d r a t e d i n t h e p r e s e n c e of 0 . 8 o r 3. 2 p e r c e n t C L S a n d 5 p e r c e n t a d d i t i v e m e n t i o n e d a b o v e . E a c h of t h e a b o v e m i x e s w a s t a k e n i n a p o l y p r o p y l e n e c o n t a i n e r a n d c o n t i n u o u s l y m i x e d o n r o l l e r s f o r 1 , 3, 7, 1 4 o r 28 d a y s . H y d r a t i o n w a s s t o p p e d a t a n y s p e c i f i e d t i m e b y t r e a t i n g t h e m i x w i t h a n e x c e s s of c o l d a b s o l u t e a l c o h o l a n d b y g r i n d i n g a n d e v a c u a t i n g f o r a d a y o v e r a l i q u i d a i r t r a p . In a l l , 7 5 s a m p l e s w e r e p r e p a r e d f o r DTA i n v e s t i g a t i o n ( T a b l e 1 ) . A n a l y s i s A l l s a m p l e s w e r e s u b j e c t e d t o DTA e x a m i n a t i o n ; s o m e w e r e a l s o e x a m i n e d b y X - r a y d i f f r a c t i o n f o r i d e n t i f i c a t i o n p u r p o s e s . DTA w a s c a r r i e d o u t u s i n g t h e D u P o n t 900 T h e r m a l A n a l y z e r . In e a c h e x p e r i - m e n t 50 m g of t h e s a m p l e p a s s i n g t h r o u g h a 1 0 0 - m e s h s i e v e w a s m o d e r a t e l y p a c k e d a n d h e a t e d a t 2 o 0 c / m i n i n a i r . S e n s i t i v i t y o n t h e AT a x i s w a s k e p t a t 0. 02 m v / i n . up t o 8 0 0 ° C , b e y o n d w h i c h i t w a s c h a n g e d t o 0. 0 0 4 m v / i n . C a l c i u m h y d r o x i d e , f o r m e d a t d i f f e r e n t p e r i o d s of h y d r a t i o n , w a s c a l c u l a t e d b y d e t e r m i n i n g i t s e n d o t h e r m a l a r e a of h y d r a t i o n b e t w e e n 450 a n d 5 5 0 ° C . T h e a m o u n t of u n h y d r a t e d .C3S a t a n y p e r i o d c o u l d b e e s t i m a t e d t h r o u g h t h e h e i g h t of t h e e n d o t h e r m a l p e a k o c c u r r i n g beyond 9 0 0 ° C owing t o r e v e r s i b l e p o l y m o r p h i c t r a n s i t i o n . In t h e d e t e r m i n a t i o n of a d s o r p t i o n - d e s o r p t i o n i s o t h e r m s t h e u n a d s o r b e d C L S i n s o l u t i o n w a s d e t e r m i n e d b y a s p e c t r o p h o t o m e t r i c m e t h o d a t a w a v e l e n g t h of 375 m p . R E S U L T S A N D DISCUSSION T h e i n f l u e n c e of a d m i x t u r e s on t h e h y d r a t i o n of C 3 S c a n b e s t u d i e d c o n v e n i e n t l y b y t h e r m a l m e t h o d s . S e q u e n t i a l s t u d i e s of C 3 S h y d r a t e d f o r d i f f e r e n t p e r i o d s h a v e y i e l d e d i m p o r t a n t d a t a on t h e k i n e t i c s of h y d r a t i o n , d e v e l o p m e n t of n e w p h a s e s a n d t h e m e c h a n i s m ( 5 - 7 ) . In t h e h y d r a t i o n of C3S t h e f o l l o w i n g e f f e c t s m a y b e o b s e r v e d : low t e m p e r a t u r e e n d o t h e r m a l p e a k s b e l o w a t e m p e r a t u r e of a b o u t 30OoC, s i g n i f y i n g t h e p r e s e n c e of c a l c i u m s i l i c a t e h y d r a t e , a n e n d o t h e r m a l e f f e c t i n t h e r a n g e of 450 t o 6 0 0 ° C i n d i c a t i n g t h e d e c o m p o s i t i o n of C a ( O H ) , , b r o a d e n d o t h e r m a l e f f e c t s f r o m 8 0 0 t o 9 0 0 ° C d u e t o d e c o m p o s i t i o n of C a C O , a n d e x p u l s i o n of w a t e r f r o m t h e h y d r a t e d s i l i c a t e , s h a r p e n d o t h e r m a l e f f e c t s b e y o n d 9 0 0 ° C o w i n g t o r e v e r s i b l e t r a n s i t i o n s i n t h e u n h y d r a t e d C 3 S a n d s o m e t i m e s a n e x o t h e r m a l p e a k i n t h e r a n g e 800 t o 9 0 0 ° C d u e t o t h e c r y s t a l l i z a t i o n of 8 - w o l l a s t o n i t e f r o m c a l c i u m s i l i c a t e h y d r a t e .In addition t o modifying t h e r a t e a t w h i c h v a r i o u s e f f e c t s o c c u r , a d d i t i v e s a n d a d m i x t u r e s m a y g e n e r a t e n e w e n d o - a n d e x o t h e r m a l e f f e c t s . T h e r a t e of h y d r a t i o n of C 3 S m a y b e followed b y e s t i m a t i n g t h e a m o u n t of Ca(OH), ( t h r o u g h t h e e n d o t h e r m a l p e a k a r e a ) f o r m e d a t d i f f e r e n t p e r i o d s of h y d r a t i o n . T h e p e a k h e i g h t of t h e e n d o t h e r m a l e f f e c t f o r t h e C3S t r a n s i t i o n b e y o n d 9 0 0 ° C m a y a l s o b e u s e d t o i n d i c a t e t h e d e g r e e of d i s a p p e a r a n c e of t h e C 3 S p h a s e . F i g u r e 1 c o m p a r e s t h e a m o u n t s of C a ( O H ) , f o r m e d i n h y d r a t i n g C 3 S i n t h e p r e s e n c e of d i f f e r e n t a d d i t i v e s . P e r t i n e n t t h e r m o g r a m s a r e a l s o p r e s e n t e d in F i g s . 2, 3 a n d 4. T r i c a l c i u m s i l i c a t e , a f t e r a d o r m a n t p e r i o d of 3 h r , h y d r a t e s a t a f a s t r a t e f o r a b o u t 3 d a y s b u t m o r e s l o w l y beyond t h i s . A t 3 d a y s n e a r l y 50 p e r c e n t of t h e C 3 S is h y d r a t e d , w h e r e a s a t 28 d a y s o n l y 7 5 p e r c e n t i s h y d r a t e d . H y d r a t i o n of C3S is s u p p r e s s e d i n t h e p r e s e n c e of 0. 8 p e r c e n t C L S e v e n u p t o 28 d a y s ( F i g s . 1A; 2, s a m p l e A-1; 3 , s a m p l e A - 2 ) . In t h e t h e r m o g r a m s , C 3 S s a m p l e s c o n t a i n i n g C L S e x h i b i t two e x o t h e r m a l h u m p s a t 360 a n d 4 2 0 ° C owing t o o x i d a t i o n e f f e c t s of t h e a d s o r b e d C L S . In a d s o r p t i o n e x p e r i m e n t s of C L S o n C 3 S i n a n a q u e o u s m e d i u m , s o m e a d s o r p t i o n m a y b e n o t e d a t low C L S c o n c e n t r a t i o n s , owing t o c o n s u m p t i o n b y t h e h y d r a t e d C3S. A t m o d e r a t e c o n c e n t r a t i o n s t h e a m o u n t of a d s o r p t i o n is m u c h l e s s b e c a u s e t h e r e is no h y d r a t i o n of C3S. A t h i g h e r C L S c o n c e n t r a t i o n s t h e a d s o r p t i o n v a l u e r i s e s owing t o t h e c r e a t i o n of m o r e s u r f a c e t h r o u g h d i s p e r s i o n of C3S p a r t i c l e s . D e s o r p t i o n e x p e r i m e n t s f r o m h i g h t o m o d e r a t e c o n c e n t r a t i o n s s h o w e d t h a t t h e d e s o r p t i o n b r a n c h d o e s n o t join t h e a d s o r p t i o n b r a n c h . A d d i t i v e s m o d i f y t h e h y d r a t i o n b e h a v i o u r of C 3 S t o s o m e e x t e n t . R a t e of h y d r a t i o n (of C 3 S ) i n t h e p r e s e n c e of C3A o r t h e h e x a g o n a l p h a s e is s o m e w h a t d i f f e r e n t ( F i g s . 1B; 1 C ; 3, s a m p l e s B - 1 , C - l ) , b e i n g r e t a r d e d s l i g h t l y a t o n e d a y a n d a c c e l e r a t e d t h e r e a f t e r . T h i s is b o r n e o u t b y C a ( O H ) , e s t i m a t i o n and b y t h e a m o u n t of C 3 S u n h y d r a t e d a t d i f f e r e n t t i m e s following c o r r e c t i o n f o r t h e a m o u n t of a d d i t i v e i n t h e C 3 S s a m p l e . DTA c u r v e s f o r s a m p l e s B - 1 a n d C-1 s h o w s i m i l a r i t y i n s h a p e c h a r a c t e r i s t i c s b e l o w 4 0 0 ° C . T h e y do not show a p e a k a t about 3 2 0 ° C o b s e r v e d f o r t h e m i x t u r e c o n t a i n i n g C3AHe ( F i g . 2, s a m p l e D-1). T h e C 3 A a n d h e x a g o n a l p h a s e s p r o b a b l y e x i s t m a i n l y a s a h e x a g o n a l p h a s e r e s u l t i n g f r o m t h e h i g h c o n c e n t r a t i o n of C a ( O H ) , i n t h e solution p h a s e . R e t a r d a t i o n of h y d r a t i o n of C 3 S c o n t a i n i n g C 3 A h a s b e e n r e p o r t e d by d e J o n g e t a 1 ( 8 ) ; C o p e l a n d a n d K a n t r o ( 9 ) , a n d C e l a n i e t a 1 ( 1 0 ) h a v e o b s e r v e d a n a c c e l e r a t o r y e f f e c t t h r o u g h o u t t h e c o u r s e of h y d r a t i o n . T h e r e t a r d a t i o n e f f e c t a t e a r l i e r p e r i o d s m a y b e e x p l a i n e d by s u b s t i t u - t i o n of ~ 1 i n t h e h i g h C/S p r o d u c t a n d p r e v e n t i o n of c o n v e r s i o n t o ~ ' low C/S h y d r a t e p r o d u c t ( r e s p o n s i b l e f o r a c c e l e r a t i o n ) . T h e a c c e l e r a t o r y e f f e c t a t l a t e r p e r i o d s i s ' n o t e a s y t o u n d e r s t a n d . P a r t of t h e e x p l a n a t i o n m a y l i e i n t h e consum'ption of C a ( O H ) , b y t h e
THERMAL ANALYSIS
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VOL. 2 259 a l u m i n a t e p h a s e s . In a d d i t i o n , t h e r a t e of s o l u t i o n a n d t h e f o r m a t i o n of A l - s u b s t i t u t e d C-S-H p r o d u c t m a y a l s o p l a y a p a r t . S e r i e s D-1 a n d E - 1 c o n t a i n i n g t h e C3AH6 a n d C-S-H p h a s e s s h o w s l i g h t r e t a r d a t i o n e f f e c t s up t o o n e d a y a n d do not a f f e c t t h e h y d r a t i o n of C 3 S a t l a t e r s t a g e s ( F i g . l D , 1 E ) . T h e c u b i c p h a s e i n p r e p a r a t i o n D-1 i s l e s s s o l u b l e t h a n t h e h e x a g o n a l p h a s e a n d d o e s n o t p r o v i d e A1 i o n s i n a n a q u e o u s m e d i u m t o c a u s e a c c e l e r a t o r y h y d r a t i o n . T h e a d d i t i o n of C - S - H r e s u l t s i n a n i n c r e a s e of C a ( O H ) , i n s o l u t i o n a n d t h u s m a y b e r e s p o n s i b l e f o r r e t a r d a t i o n e f f e c t s . T h e d e g r e e of h a r d n e s s of t h e s e t i n t h e a b o v e s a m p l e s s h o w s s o m e c o r r e l a t i o n w i t h t h e o b s e r v e d d e g r e e of h y d r a t i o n ( T a b l e 1 ) . A s a l r e a d y shown, h y d r a t i o n of C3S i s s u p p r e s s e d i n t h e p r e s e n c e of 0 . 8 p e r c e n t CLS. An a d d i t i o n of o n l y 5 p e r c e n t C,A i s s u f f i c i e n t t o p r o m o t e s i g n i f i c a n t h y d r a t i o n a t 3 d a y s and beyond ( F i g s . 1B; 3, s a m p l e B - 2 ) . When a n a q u e o u s s o l u t i o n of CLS c o m e s i n t o c o n t a c t with a m i x t u r e of C,A a n d C,S i t a p p e a r s t h a t only a s m a l l a m o u n t of C L S i s t a k e n u p b y C3S i n c o m p a r i s o n w i t h t h a t t a k e n up b y C3A. It h a s b e e n s h o w n t h a t C3A c a n c o n s u m e l a r g e q u a n t i t i e s of C L S i n a n a q u e o u s m e d i u m ( 4 ) . T h e c o m p l e x s e e m s t o f o r m f i r s t o n t h e s u r f a c e of C3A, a n d s u b s e q u e n t l y i s a c c e l e r a t e d i n t h e b u l k p h a s e . In t h e C3S-C3A-CLS-H,O s y s t e m a n u p t a k e of C L S b y C,A r e s u l t s i n a c o n t i n u o u s d e c r e a s e of C L S i n t h e s o l u t i o n p h a s e .In
d i l u t e C L S s o l u t i o n s C 3 S t e n d s t o h y d r a t e owing t o t h e d i s s o l u t i o n of t h e a d s o r b e d C L S i n t o t h e s o l u t i o n p h a s e . T h e r a t e of h y d r a t i o n of C3S i s d e t e r m i n e d b y t h e r e l a t i v e r a t e s , a m o u n t s and m e c h a n i s m s t h r o u g h w h i c h C L S i s c o n s u m e d b y C3A o r C3S. If a l a r g e r a m o u n t of C L S i s p r e s e n t i n t h e C3S-C3A-H,O m i x , t h e h y d r a t i o n of C3S i s n e g l i g i b l e e v e n a t 1 4 d a y s . T h i s m e a n s t h a t i t t a k e s l o n g e r f o r C3A t o c o n s u m e a l a r g e r a m o u n t of C L S ( F i g s . 1B; 3, s a m p l e B - 3 ) . T h e h e x a g o n a l p h a s e i s m o r e e f f i c i e n t i n i n h i b i t i n g t h e h y d r a t i o n of C3S t h a n C3A i n t h e C3S-CLS-H,O s y s t e m ( F i g s . 1C; 4, s a m p l e C - 2 ) E a r l i e r w o r k s h o w e d t h a t t h e h e x a g o n a l p h a s e i r r e v e r s i b l y a d s o r b s C L S t o a l e s s e r e x t e n t a n d m o r e s l o w l y t h a n t h e C 3 A p h a s e ( 4 ) . At a n y c o n c e n t r a t i o n l e v e l of CLS, m o r e C L S i s l e f t i n t h e s o l u t i o n p h a s e i n t h e p r e s e n c e of t h e h e x a g o n a l p h a s e t h a n i s l e f t with C3A. H e n c e t h e h e x a g o n a l p h a s e i n h i b i t s h y d r a t i o n of C3S t o a g r e a t e r e x t e n t . H y d r a t i o n i s c o n s i d e r a b l e a t 28 d a y s w h e n a s u b s t a n t i a l q u a n t i t y of C L S i s c o n s u m e d b y t h e h e x a g o n a l p h a s e t h r o u g h c o m p l e x f o r m a t i o n and p r e c i p i t a t i o n . At a l a r g e r C L S c o n t e n t t h e h e x a g o n a l p h a s e i n h i b i t s t h e h y d r a t i o n of C,S ( F i g s . 1C; 4, s a m p l e C - 3 ) . T h e c u b i c p h a s e (C3AH,) a d s o r b s m i c h l e s s C L S t h a n t h e h e x a g o n a l p h a s e ( F i g . 5 ) . T h i s i s a l s o e v i d e n t f r o m t h e c o m p l e t e a b s e n c e of h y d r a t i o n of C3S with t h e a d d i t i o n of 5 p e r c e n t of t h e c u b i c p h a s e ( F i g s . I D ; 4, s a m p l e D-2). A s m a l l a m o u n t of a d s o r p t i o n b y C3AH, does n o t c h a n g e t h e c o n c e n t r a t i o n of C L S i n t h e s o l u t i o n t o a n y s i g n i f i c a n t e x t e n t t o d i s t u r b t h e a d s o r b e d C L S l a y e r o n t h e C 3 S s u r f a c e . T h e a d d i t i o n of H - C 3 S a l s o i n h i b i t s h y d r a t i o n of C3S i n t h e C3S-CLS-H,Os y s t e m but not t o t h e s a m e e x t e n t a s C3AH, ( F i g s . 1 E , 1D; 4, s a m p l e s D - 2 , E - 2 ) . P r e l i m i n a r y r e s u l t s s h o w t h a t H-C,S i r r e v e r s i b l y a d s o r b s C L S t o s o m e e x t e n t a l t h o u g h not enough t o p r o m o t e h y d r a t i o n of C 3 S . T h e p r o g r e s s of h y d r a t i o n is a l s o r e f l e c t e d i n t h e n a t u r e of t h e h y d r a t e d p r o d u c t ( T a b l e 1 ) . T h e m i x C 3 S - C L S - H 2 0 is a l w a y s fluid, s i n c e t h e r e i s no h y d r a t i o n of C3S. A d d i t i o n of C3S p r o m o t e s f o r m a t i o n of a h a r d m a s s a f t e r s o m e d a y s . T h e a d d i t i o n of t h e h e x a g o n a l p h a s e d o e s n o t m a k e t h e m a s s h a r d t i l l 28 d a y s . T h e s e t r e m a i n s v e r y s o f t w i t h t h e a d d i t i v e s C3AH, a n d H-C,S, a s m i g h t b e e x p e c t e d . In p o r t l a n d c e m e n t s B r u e r e ( 1 1 ) a n d D o d s o n a n d F a r k a s ( 1 2 ) h a v e o b s e r v e d t h a t h y d r a t i o n is r e t a r d e d t o a g r e a t e r e x t e n t i f c a l c i u m l i g n o s u l f o n a t e i s a d d e d t o t h e p a s t e t h a t i s p r e h y d r a t e d f o r 5 m i n . t h a n if i t i s d i r e c t l y p r e s e n t in t h e m i x i n g w a t e r . It i s p o s t u l a t e d t h a t t h i s i s d u e t o s t r o n g e r a d s o r p t i o n of C L S on t h e C,A p h a s e t h a n on t h e - c a l c i u m s u l f o a l u m i n a t e - c o a t e d C 3 A . A c o m p a r i s o n of t h e r a t e of h y d r a - t i o n i n s e r i e s B - 4 a n d B - 2 s h o w s t h a t if C3S
+
C,A is p r e h y d r a t e d f o r 5 m i n . a n d C L S i s a d d e d , t h e h y d r a t i o n w i l l b e v e r y s t r o n g l y r e t a r d e d u p t o a b o u t 7 d a y s ( F i g s . 1B; 3 , s a m p l e s B - 2 , B - 4 ) . D i r e c t h y d r a t i o n of C 3 S - C 3 A - C L S - H 2 0 s h o w s a c c e l e r a t i o n of C 3 S h y d r a t i o n f r o m 3 d a y s o n w a r d . T h i s m a y b e m a i n l y d u e t o t h e f o r m a t i o n w i t h i n 5 m i n . of t h e h e x a g o n a l a n d c u b i c p h a s e s of c a l c i u m a l u m i n a t e h y d r a t e s , w h i c h c o n s u m e l e s s C L S t h a n C 3 A . It i s a l s o q u i t e p o s s i b l e t h a t d u r i n g p r e h y d r a t i o n C 3 S f o r m s a c o a t i n g of a h y d r a t i o n c o m p l e x w i t h C L S m o r e r e s i s t a n t t o h y d r a t i o n . F i g u r e s 1 F ; 3 , s a m p l e B - 6 ; 4, s a m p l e B - 5 , s h o w t h a t C 3 S s a m p l e s p r e h y d r a t e d f o r 5 m i n . o r o n e d a y s h o w t h e s a m e b e h a v i o u r in s l i g h t l y r e t a r d i n g h y d r a t i o n up t o 3 d a y s w h e n c o m p a r e d w i t h C 3 S s a m p l e s d i r e c t l y h y d r a t e d w i t h C3A a n d CLS. A C K N O W L E D G E M E N T S T h a n k s a r e d u e t o t h e e x p e r i m e n t a l c o n t r i b u t i o n of G. M. P o l o m a r k . R E F E R E N C E S 1. P . S e l i g m a n a n d N. R . G r e e n i n g , H i g h w a y R e s e a r c h R e c o r d , 62, 8 0 ( 1 9 6 4 ) . 2. J. F. Young, J. A m e r . C e r a m . S o c . ,52,
4 4 ( 1 9 6 9 ) . 3 . V. S . R a m a c h a n d r a n a n d R. F. F e l d m a n , " A d s o r p t i o n of C a l c i u m L i g n o s u l f o n a t e o n T r i c a l c i u m A l u m i n a t e a n d i t s H y d r a t e s i n a Non-Aqueous M e d i u m " ( t o b e p u b l i s h e d ) . 4. V. S . R a m a c h a n d r a n and R. F. F e l d m a n , "Effect of C a l c i u m L i g n o s u l f o n a t e on T r i c a l c i u m A l u m i n a t e a n d I t s H y d r a t i o n P r o d u c t s ' ' ( t o b e p u b l i s h e d ) .T H E R M A L ANALYSIS
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VOL. 2 26 1 5. V. S. R a m a c h a n d r a n , "Applications of DTA i n C e m e n t C h e m i s t r y , I ' C h e m i c a l P u b l i s h i n g C o . , New Y o r k , 1969. 6. V . S . R a m a c h a n d r a n , T h e r m o c h i m i c a A c t a ,2 ,
41 (1971). 7. V. S . R a m a c h a n d r a n , M a t e r i a u x e t C o n s t r u c t i o n ,4
, 3 (197 1). 8. J. G . M. deJong, H. N. S t e i n a n d J. M. S t e v e l s , P r o c . 5th Int. S y m p . C h e m . C e m . , Tokyo,2 ,
311 (1968). 9. L. E. Copeland, a n d D. L. K a n t r o , Ibid, 387. 10. A. C e l a n i , P. A. Moggi, and A. Rio, Ibid, 492.11. G. M. B r u e r e , Highway R e s e a r c h B o a r d , S p e c i a l R e p o r t 90, 26, (1966). 12. V. H. Dodson a n d E. F a r k a s , A m e r i c a n S o c i e t y f o r T e s t i n g a n d M a t e r i a l s , W c . ,
64,
816 (1964). T h i s p a p e r is a c o n t r i b u t i o n f r o m t h e D i v i s i o n of Building R e s e a r c h , N a t i o n a l R e s e a r c h Council of C a n a d a , a n d is p u b l i s h e d with t h e a p p r o v a l of t h e D i r e c t o r of t h e Division.T A B L E 1 D E T A I L S O F S A M P L E P R E P A R A T I O N AND T H E I R HARDENING C H A R A C T E R I S T I C S A d d i t i v e s = 57'0, C a l c i u m L i g n o s u l f o n a t e = 0. 8 o r 3. 2% w a t e r / s o l i d = 0. 6 F = fluid, S = s o f t , MH = m e d i u m h a r d , H = h a r d S a m p l e D e s i g
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n a t i o n A - 1 A - 2 B - 1 B - 2 B -3 B - 4 B - 5 B - 6 C - 1 C - 2 C - 3 D-1 D-2 E - 1 E - 2 S a m p l e P r e p a r a t i o n C , S t H 2 0 C,S+CLS(O. 8 7 0 ) + H 2 0 C , S + C , A + H 2 0 C,S+C,A+CLS(O. 8 7 0 ) + H 2 0 C,S+C,A+CLS(3. 270)+H20 C , S + C , A ( h y d r a t e d 5 m i n ) + C L S ( 0 . 8 7 0 ) t H 2 0 C,S+CLS(O. 8 7 0 ) h y d r a t e d 5 min+C,A+H,O C,S+CLS(O. 8 7 0 ) h y d r a t e d 1 day+C,A+H,O C,S+(C4AH - C 2 A H )+H,O X X C,S+(C,AH -C,AH )+ X X C L S ( 0 . 8 7 0 ) + H 2 0 C,S+(C4AH -C,AH )+ X X C L S ( 3 . 2%)+H2 0 C,S+C,AH,+H,O C,S+C,AH,+CLS(O. 8 % ) + H z o C,S+(H-C,S)+H,O C,S+(H-C,S)+CLS(O. 8 % ) + H 2 ° N a t u r e and C o n s i s t e n c y of t h e S e t 1 S F S F F S S F S F F S F S F i n d a y s 1 4 H F H H S MH H MH H F F H F MH F 28 H F H H H H H H H MH S H S H S ( A r b i t r a r y ) 3 MH F H S F S S S MH F F S F MH F - 7 MH F H H S S MH S MH F F MH F MH FTHERMAL ANALYSIS
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